the 15" has a lower fs ,more power and xmax.you should get lower bass for movies.you really should be looking at subwoofers and not woofers for movies.but if money is really tight you can't go wrong with the daytons

For what you want to do this would be much better for the money Id probaly go with one of these with the amp you have This would be much more suited for movies as it is a subwoofer It has almost twice the xmax of the previously mentioned wooffer and a fs of 25 hz In the proper enclosure this would give you your requested bang for the buck.

I also failed to mention that the efficiency of the shielded dvc 12 is 94 db compared to 91 for th eclassic wooffer this along with the xmax advantage maeans that 1 shielded dvc 12 would be very comparable (on the same 150 watts ) to 2 classic 12 inch woofers and probalby much better suited for a subwoofer and cheaper